POACEAE 65 



23. Andropogon Tennesse6nsis Scribn. Stems 1-1.5 m. tall, stout, the branches 

 in 1's or 2's : leaf-sheaths, at least the lower ones, hirsute toward the summit ; blades 6 

 dm. long or less, 6-1 2 mm. wide, rough, the lower surface sometimes hirsute, and also the 

 upper surface near the base : racemes in 2's-4's, 5-8 cm. long : sessile spikelet about 8.5 

 mm. long, broadly lanceolate, twice as long as the hispidulous internode, the outer 2 

 scales strongly hispidulous, the awn of the fourth scale geniculate, about 1.5 cm. long, 

 twisted below, the column a little exserted ; pedicellate spikelet 8-10 mm. long, of 4 scales, 

 perfect, the outer 2 scales strongly hispidulous, the first often short-awned, the hispidulous 

 pedicel less than ^ as long as the sessile spikelet. 



In dry soil, Tennessee and Mississippi. Fall. 



24. Andropogon geminatus Hack. Smooth and glabrous, glaucous. Stems 6-10 

 dm. tall, from long rootstocks : leaf-blades erect, rigid, long-acuminate, 3 dm. long or 

 less, 9 mm. wide or less : racemes in pairs, finally exserted, 3-5 cm. long, rather slender, 

 the hairs on the rachis-internodes and the pedicels grayish or yellowish white : sessile 

 spikelet 6-8 mm. long, the awn not twisted below, geniculate, 5-7 mm. long ; pedicellate 

 spikelet about the same length, awnless. 



In dry soil, Texas. Summer. 



10. AMPHILOPHIS Nash. 



Perennial grasses, with usually flat leaf-blades and showy often silvery white panicles, 

 the axis short, making the panicle appear fan-like, or elongated with the branches scattered. 

 Racemes usually numerous, the internodes with manifestly thickened margins, the median 

 portion thin and translucent, the pedicels of the same construction, the margins ciliate 

 with usually long hairs. Sessile spikelets of 4 scales, the first one 2-keeled, the second 

 1-keeled, the third and fourth scales hyaline, the latter very narrow, stipe-like, somewhat 

 thickened, gradually merging into a usually geniculate contorted or spiral awn, or the awn 

 rarely wanting. Pedicellate spikelets staminate and similar to the sessile, or sterile and 

 smaller than them. Stamens 3. Styles distinct. Stigmas plumose. 



First scale of the sessile spikelet not pitted on the back. 



Axis of the panicle elongated, the branches scattered, the panicle hence linear 



to oblong ; stem-nodes naked. 

 Sessile spikelets 3 mm. long, the awn wanting or rarely present and then but 



short and not twisted. 1. A. exaristatus. 



Sessile spikelets 4 mm. long, the awn long and geniculate, spiral at the base. 2. A. Torreyanus. 

 Axis of the panicle short, the branches congested, the panicle hence fan-like, 



oval or obovate ; stem-nodes densely barbed. 3. A. barbinodis. 



First scale of the sessile spikelet with a deep pit-like impression on the back. 4. A. perforatus. 



1. Amphilophis exaristatus Nash. Smooth and glabrous. Stems 6-8 dm. tall, rather 

 slender : leaf -blades 2 dm. long or less, 3-6 mm. wide, rough toward the apex : panicle 

 10-13 cm. long, 2-2.5 cm. wide, oblong, its axis 8-10 cm. long, the branches much divided, 

 the ultimate divisions (racemes) 1-2 cm. long, the terminal hairs 2-3 times as long as the 

 rachis-internodes : sessile spikelet 3 mm. long, about again as long as the internode, 

 the fourth scale almost wanting, or present as a mere rudiment, very rarely short-awned ; 

 pedicellate spikelet of a single scale, 2-3 mm. long, the pedicel considerably shorter than 

 the sessile spikelet. [Andropogon saccharoides submuticusVasey, not A. submuticus Steud.] 



In dry soil, Texas. Summer. 



2. Amphilophis Torreyanus (Steud. ) Nash. Smooth and glabrous, glaucous. Stems 

 5-10 dm. tall, simple or somewhat branched : leaf-blades 1-5 dm. long or less, 3-7 mm. 

 wide, rough above : panicle 4-10 cm. long, 7-20 mm. wide, linear to oblong, its axis 2-7 

 cm. long, the longer branches somewhat divided, the ultimate divisions (racemes) 1-4 cm. 

 long, the terminal hairs 1J-2 times as long as the internodes : sessile spikelet 4 mm. long, 

 about % again as long as the internode, the awn geniculate, more or less contorted, 10-15 

 mm. long, spiral at the base, the column much exserted; pedicellate spikelet consisting of 

 a single scale, 2-3 mm. long, the pedicel shorter than the sessile spikelet. 



In dry soil, Kansas to Arizona, Texas and Mexico. Summer. 



3. Amphilophis barbinodis (Lag.) Nash. Stems tufted, 5-10 dm. tall, simple or 

 somewhat branched, the nodes densely barbed with silvery hairs : leaf-sheaths and their 

 blades smooth and glabrous, the latter 2 dm. long or less/ 2-8 mm. wide, rough : panicle 

 broadly oblong, ovate, oval or obovate, 5-12 cm. long, finally exserted, its axis 2-5 cm. 

 long : racemes 2-15, 3-5 cm. long, the terminal hairs twice as long as the internodes : ses- 

 sile spikelet 5-6 mm. long, about again as long as the internode, the geniculate awn 

 2-3 cm. long, spiral at the base, the column much exserted ; pedicellate spikelet of a single 

 awnless scale, 4-5 mm. long, the pedicel considerably shorter than the sessile spikelet. 



In moist or rocky ground, central Texas to Arizona and Mexico. Summer and fall. 

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